Prepare the sushi rice by folding in rice vinegar and sea salt while warm, then let cool to room temperature.
Slice the sushi-grade salmon into long, thin strips and butterfly the cooked shrimp by slicing down the back without cutting all the way through.
Julienne the cucumber into thin matchsticks and thinly slice the avocado.
Place a nori sheet on a bamboo rolling mat and spread a thin, even layer of rice over two-thirds of the sheet, leaving the top edge clear.
Arrange the salmon, shrimp, cucumber, and avocado in a horizontal line across the center of the rice.
Roll the sushi tightly using the mat, sealing the top edge with a small dab of water.
Use a very sharp, wet knife to slice the roll into eight even, bite-sized pieces.
Serve immediately with coconut aminos, wasabi, and pickled ginger on the side.